1) A molecular replacement solution of the crystal structure of the Fab of CC49, a murine monoclonal antibody against solid adenocarcinoma, has been refined at 3.5-Angstrom resolution. 2) A molecular replacement solution of the crystal structure of the Fab of TR1.9, a human autoantibody that binds to thyroid peroxidase, has been obtained and is being refined at 2.2-Angstrom resolution. 3) Crystals of a murine T-cell receptor alpha-chain variable domain have been obtained, x-ray data have been collected to 2.8-Angstrom resolution, and the determination of the structure by molecular replacement is in progress. 4) Crystallization of several proteins, including tyrosine hydroxylase, the extracellular domain of the alpha-chain and the intracellular domain of the gamma-chain of the human high-affinity receptor for IgE, and the Fab of the galactan-binding murine antibody X24, is being attempted.